Exploring Predictors of Self-Perceived Cardiorespiratory Fitness ≥ 5 Years Beyond Breast Cancer Diagnosis: A Cross-Sectional Study

<b>Background/Objectives</b>: This study aimed to examine the association between self-perceived cardiorespiratory fitness and health outcomes in long-term breast cancer survivors (LTBCSs) and identify possible predictors in women at least 5 years post-diagnosis. <b>Methods</b>: A cross-sectional study was carried out involving 80 LTBCSs, divided into three groups according to their self-reported cardiorespiratory fitness levels: very poor/poor (1-2), average (3), and good/very good (4-5). Sociodemographic and clinical data were collected, and this study analyzed variables measured at least five years after diagnosis, focusing on various factors including physical fitness, physical activity (PA) levels, cancer-related fatigue (CRF), mood, pain, and health-related quality of life (HRQoL). ANOVA, Mann-Whitney U, and chi-square tests were performed, along with correlation and multiple regression analyses. Cohen's <i>d</i> was used to calculate effect sizes. <b>Results</b>: Among the 80 LTBCSs, 35% reported very poor/poor self-perceived cardiorespiratory fitness, 35% reported average levels, and 30% reported good/very good levels. Individuals with lower self-perceived cardiorespiratory fitness levels showed significant declines in physical fitness, greater physical inactivity, increased CRF, higher pain levels, and a poorer HRQoL (<i>p</i> < 0.05). Regression analysis identified "self-perceived muscle strength" (β = 0.40; <i>p</i> < 0.01) and "nausea and vomiting" (β = -0.37; <i>p</i> < 0.01) as significant predictors of higher self-perceived cardiorespiratory fitness (adjusted r² = 0.472). <b>Conclusions</b>: These findings highlight the importance of self-perceived cardiorespiratory fitness as a relevant indicator of health outcomes in LTBCSs. Given its association with physical fitness, sedentary behavior, CRF, pain, and HRQoL, assessing patients' perceptions may provide valuable insights for developing tailored rehabilitation strategies. Future interventions should consider both subjective and objective measures to optimize the long-term health and quality of life in this population.